This invention pertains to keyboards and, in particular, to keyboards for accessing or actuating indicia associated with the keyboard keys.
Keyboards are used in numerous applications for accessing or actuating representations or indicia associated with the keyboards keys. Thus, for example, in typewriters of the mechanical or electrical type, the typewriter keys enable mechanical and electrical actuation, respectively, of printing heads carrying alphaneumeric indicia associated with the keys. Analagously, in computer video terminals, computer teleprinters and electronic calculators, keyboard keys enable accessing of related indicia for display and other purposes.
During the use of a keyboard it is often necessary to repeatedly access the same indicium, thereby requiring repeated striking of the corresponding keyboard key. This occurs, for example, if printing or displaying of a word having repeated letters, such as, e.g., the word root, is required. It also occurs when a lengthy passage is to be underlined or underscored as might happen when using a typewriter. Continued movement of a cursor on a computer video terminal also requires a similar repetitive key striking.
In order to avoid multiple striking of the same key, keyboard systems have been developed which possess what is commonly referred to as an "automatic repeat capability." Such a capability enables continuous accessing of an indicium without multiple key striking. In one form, this capability is provided by holding a key in the struck position until the corresponding indicium is accessed the desired number of times. In another form, a separate so called "repeat key" is provided. When multiple access is desired, the latter key is depressed along with the key whose indicium is desired, and as long as both keys are depressed the desired indicium is repeatedly accessed.
A further improvement over the aforesaid automatic repeat keyboard systems is one having variable speed operation. With this type of automatic repeat, accessing of the indicium corresponding to a struck key can be rapid or slow at the operator's option. Thus, if only a few repetitions are required slow repeat can be selected to enable the operator to release the struck key when the required number of the repetitions has occurred. On the other hand, if a large number of repetitions are required, initial repeat can be at a rapid pace and the pace thereafter slowed so as to again permit accurate release of the struck key when the desired number of repetitions has occurred.
To date, variable automatic repeats for keyboard operation have been limited to the use of mechanically operated actuators for realizing the variable repeat function. Thus, a variety of graphics terminals are equipped with so called "joy sticks" or "track balls" for obtaining variable automatic repeat. In these instances, mechanical movement of the respective element is used to generate an electrical signal which varies with the degree of movement. This variable signal is then used to correspondingly vary the repeat function. Another form of variable automatic repeat utilizes a separate keyboard key which upon being held in the struck position varies the repeat rate of the indicium already undergoing repetition.
The aforesaid variable automatic repeats have certain detracting qualities. Thus, the joy stick and track ball require continued mechanical movement, and, therefore, are susceptible to costly mechanical breakdowns. Moreover, they require two handed operation. The use of these devices has thus been confined primarily to cursor positioning, i.e., to movement of an indicator showing where the next accessed indicium is to be placed. Similar deficiences are attendant the separate key variable automatic repeat. The latter repeat also suffers the disadvantage of being incapable of continuous variation in repetition rate. Only two discrete operating rates, one fast and the other slow, are possible.
It is therefore a primary object of the present invention to provide an improved keyboard system.
It is a further object of the present invention to provide a keyboard system having an electronically actuated variable automatic repeat requiring only single handed operation.